The present invention relates to an engine ignition interpolation apparatus for interpolating reference position signals when no outputs are issued from engine reference position sensors used in engine ignition control.
Recent rapid developments in electronics technology have resulted in an increased tendency for engine ignition timing to be controlled by a digital system. For example, an electronic engine ignition control circuit for two-wheeled motorcycles is supplied with crank angle pulses generated each time a crank shaft rotates through a unit angle and reference positions pulses representing positions of pistons in respective cylinders. The control circuit counts and processes the crank angle pulses with the reference position pulses being used as references for determining a dwell angle and for controlling ignition timing.
The crank angle pulses are produced by a crank angle sensor which detects teeth cut at a pitch of two degrees around the outer periphery of a crank angle rotor mounted on the crank shaft. The reference position pulses are generated by reference position sensors which correspond respectively to the cylinder pistons and are disposed around the periphery of a reference position rotor mounted on the crank shaft.
A problem with prior engine ignition control systems is that when the reference position sensors or a system for transmitting outputs therefrom fails, normal sensor outputs are not delivered and those cylinders which correspond to the faulty reference position sensors cannot have their ignition timing properly controlled.